Fertility Preservation by Embryo Banking (Embryo Freezing)

Overview

Embryo banking (embryo freezing) is the most well established method of fertility preservation with the largest amount of outcome data published in the literature. Successfully used for decades, embryo freezing has been responsible for births of hundreds of thousands of babies worldwide.

Embryo freezing requires a woman to undergo ovarian stimulation. In a natural menstrual cycle, only one mature egg is usually released from the ovary for possible fertilization. In embryo freezing, the patient takes daily hormonal injections that encourage the ovaries to develop multiple mature eggs. When these eggs are ready, they are retrieved with a thin needle inserted into the ovary under ultrasound control via the vagina. The patient is usually asleep for this procedure under intravenous sedation given by an anesthesiologist, which takes only a few minutes.

Retrieved eggs are mixed with partner’s (or donor’s) sperm for fertilization, and embryos are created. The embryos are cultured for a few days, and then frozen for future use.

Who May Benefit from Embryo Freezing

Embryo freezing is a routine procedure for both medical and social fertility preservation (unlike egg freezing, which is considered experimental if performed for social reasons). Because embryo freezing requires sperm, embryo freezing may not be a good option for women who do not have a committed partner. Many single women, for this reason, choose egg freezing instead. Embryo freezing, however, is still the best and most established method of social fertility preservation for couples in stable relationships.

Embryo freezing takes a few weeks to complete. Some newly diagnosed cancer patients may not have enough time before they are scheduled to undergo chemotherapy or radiation to freeze embryos (or eggs). Even when patients have enough time for an embryo freezing cycle, a single embryo freezing cycle may not suffice to freeze enough embryos.

The literature suggests that cancer patients typically produce only approximately eight embryos per cycle, which may not be enough to offer a high probability of future pregnancy. Other fertility preservation methods such as ovarian tissue cryopreservation may be a better option, depending on the treatment time frame.

How Many Embryos to Freeze

With a decades-long history, embryo freezing has considerable outcome data to determine how many embryos should be frozen in order to have a reasonable chance of future pregnancy. How many embryos a patient should freeze will depend on her age and ovarian reserve status. For younger women with normal ovarian reserve, CHR typically recommends freezing of at least 20 embryos. As embryos frozen later in life have a lower potential of leading to a pregnancy, women in their 30s and 40s should consider freezing significantly more. CHR physicians will counsel patients based on their individual circumstances.